Upper electrode backing member with particle reducing features

ABSTRACT

Components of a plasma processing apparatus includes a backing member with gas passages attached to an upper electrode with gas passages. To compensate for the differences in coefficient of thermal expansion between the metallic backing member and upper electrode, the gas passages are positioned and sized such that they are misaligned at ambient temperature and substantially concentric at an elevated processing temperature. Non-uniform shear stresses can be generated in the elastomeric bonding material, due to the thermal expansion. Shear stresses can either be accommodated by applying an elastomeric bonding material of varying thickness or using a backing member comprising of multiple pieces.

RELATED APPLICATIONS

This application claims priority under 35 U.S.C. 119 to U.S. ProvisionalApplication No. 60/851,745 entitled UPPER ELECTRODE BACKING MEMBER WITHPARTICLE REDUCING FEATURES and filed on Oct. 16, 2006, the entirecontent of which is hereby incorporated by reference.

BACKGROUND

Plasma processing apparatuses are used to process substrates bytechniques including etching, physical vapor deposition (PVD), chemicalvapor deposition (CVD), ion implantation, and resist removal. One typeof plasma processing apparatus used in plasma processing includes areaction chamber containing upper and bottom electrodes. An electricfield is established between the electrodes to excite a process gas intothe plasma state to process substrates in the reaction chamber.

SUMMARY

A component for a plasma processing apparatus for processingsemiconductor substrates is provided. In a preferred embodiment, thecomponent includes a first member bonded to a second member. The firstmember includes a plurality of first through openings, a plasma-exposedsurface and a first coefficient of thermal expansion. The second memberattached to the first member includes a plurality of second throughopenings corresponding to the openings in the first member, the secondmember and having a second coefficient of thermal expansion greater thanthe first coefficient of thermal expansion. The first and secondopenings are misaligned at ambient temperature and the openings in thefirst member and the openings in the second member are substantiallyconcentric when heated to an elevated processing temperature.

In a preferred embodiment, the component is a showerhead electrodeassembly for a plasma processing apparatus.

A preferred embodiment of the showerhead electrode assembly for a plasmaprocessing apparatus includes a silicon inner electrode with aplasma-exposed surface, the electrode having a plurality of axial gasdistribution passages. A metallic backing member is bonded to theelectrode and includes a plurality of axial gas distribution passagescorresponding to the passages in the electrode. The passages in thebacking member are radially larger than the passages in the electrode,to reduce the exposure of second member to a plasma environment. Thepassages in the electrode and the passages in the backing member aremisaligned at ambient temperature and the passages in the electrode andthe passages in the backing member are substantially concentric whenheated to an elevated processing temperature.

Another preferred embodiment provides a method of processing asemiconductor substrate in a plasma processing apparatus. A substrate isplaced on a substrate support in a reaction chamber of a plasmaprocessing apparatus. A process gas is introduced into the reactionchamber with the showerhead electrode assembly. A plasma is generatedfrom the process gas in the reaction chamber between the showerheadelectrode assembly and the substrate. The substrate is processed withthe plasma.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a portion of an embodiment of a showerhead electrodeassembly and a substrate support for a plasma processing apparatus.

FIG. 2A illustrates a plan view of a circular backing member.

FIG. 2B is an enlarged plan view of FIG. 2A, including gas passages atan ambient temperature.

FIG. 2C is an enlarged plan view of FIG. 2A, including gas passages atan elevated processing temperature.

FIG. 2D is an enlarged plan view of FIG. 2A, including gas passages at amaximum processing temperature.

FIG. 3 is an enlarged plan view of FIG. 2A, depicting a non-circular gaspassage.

FIG. 4 is a cross-sectional view of the backing member attached to upperelectrode, including an elastomeric bonding material and conductivemember.

FIG. 5 is a cross-sectional view of the backing member attached to upperelectrode, including a raised peripheral edge to reduce the exposure ofthe elastomeric bonding material to a plasma environment.

FIG. 6 is a cross-sectional view of backing member and upper electrode,including an elastomeric bonding material having a non-uniformthickness.

FIG. 7A illustrates a plan view of the backing member, comprisingmultiple pieces forming a segmented concentric ring.

FIG. 7B illustrates a plan view of the backing member, comprisingmultiple pieces having hexagonal-shapes.

FIG. 8 illustrates a cross-sectional view of backing member, includingthicker segments connected by thinner flexure segments.

DETAILED DESCRIPTION

Control of particulate contamination on the surfaces of semiconductorwafers during the fabrication of integrated circuits is essential inachieving reliable devices and obtaining a high yield. Processingequipment, such as plasma processing apparatuses, can be a source ofparticulate contamination. For example, the presence of particles on thewafer surface can locally disrupt pattern transfer duringphotolithography and etching steps. As a result, these particles canintroduce defects into critical features, including gate structures,intermetal dielectric layers or metallic interconnect lines, resultingin the malfunction or failure of the integrated circuit component.

FIG. 1 illustrates an embodiment of a showerhead electrode assembly 10for a plasma processing apparatus in which semiconductor substrates,e.g., silicon wafers, are processed. The showerhead electrode assemblyis also described, for example, in commonly-owned U.S. PatentApplication Publication No. 2005/0133160, which is incorporated hereinby reference in its entirety. The showerhead electrode assembly 10comprises a showerhead electrode including an upper electrode 12, abacking member 14 secured to a thermal control plate 16. A substratesupport 18 (only a portion of which is shown in FIG. 1) including abottom electrode and optional electrostatic clamping electrode ispositioned beneath the upper electrode in the vacuum processing chamberof the plasma processing apparatus. A substrate 20, subjected to plasmaprocessing, is mechanically or electrostatically clamped on an uppersupport surface 22 of the substrate support 18.

The upper electrode 12 can be electrically grounded, or alternativelycan be powered, preferably by a radio-frequency (RF) current source. Ina preferred embodiment, the upper electrode 12 is grounded, and power atone or more frequencies is applied to the bottom electrode to generateplasma in the plasma processing chamber. For example, the bottomelectrode can be powered at frequencies of 2 MHz and 27 MHz by twoindependently controlled radio frequency power sources. After asubstrate 20 has been processed (e.g., a semiconductor substrate hasbeen plasma etched), the supply of power to the bottom electrode is shutoff to terminate plasma generation.

In the illustrated embodiment, the upper electrode 12 of the showerheadelectrode includes an inner electrode member 24, and an optional outerelectrode member 26. The inner electrode member 24 is preferably acylindrical plate (e.g., a plate composed of silicon). The innerelectrode member 24 can have a diameter smaller than, equal to, orlarger than a wafer to be processed, e.g., a diameter up to 12 inches(300 mm) if the plate is made of single crystal silicon. In a preferredembodiment, the showerhead electrode assembly 10 is large enough forprocessing large substrates, such as semiconductor wafers having adiameter of 300 mm or larger. For 300 mm wafers, the upper electrode 12is at least 300 mm in diameter. However, the showerhead electrodeassembly 10 can be sized to process other wafer sizes or substrateshaving a non-circular configuration. In the illustrated embodiment, theinner electrode member 24 is wider than the substrate 20. For processing300 mm wafers, the outer electrode member 26 is provided to expand thediameter of the upper electrode 12 from, for example, about 15 inches toabout 17 inches. The outer electrode member 26 can be a continuousmember (e.g., a continuous poly-silicon ring), or a segmented member(e.g., including 2-6 separate segments arranged in a ring configuration,such as multiple segments composed of silicon). In embodiments of theupper electrode 12 that include a multiple-segment, outer electrodemember 26, the segments preferably have edges, which overlap each otherto protect an underlying bonding material from exposure to plasma. Theinner electrode member 24 preferably includes multiple gas passages 28extending through and in correspondence with multiple gas passages 30formed in the backing member 14 for injecting process gas into a spacein a plasma reaction chamber located between the upper electrode 12 andthe substrate support 18.

Silicon is a preferred material for plasma exposed surfaces of the innerelectrode member 24 and the outer electrode member 26. High-purity,single crystal silicon minimizes contamination of substrates duringplasma processing, and also wears smoothly during plasma processing,thereby minimizing particles. Alternative materials that can be used forplasma-exposed surfaces of the upper electrode 12 include SiC or AlN,for example.

In the illustrated embodiment, the backing member 14 includes a backingplate 32 and a backing ring 34 extending around the periphery of backingplate 32. In the embodiment, the inner electrode member 24 isco-extensive with the backing plate 32, and the outer electrode member26 is co-extensive with the surrounding backing ring 34. However, inanother embodiment, the backing plate 32 can extend beyond the innerelectrode member 24 such that a single backing plate can be used tosupport the inner electrode member 24 and the segmented outer electrodemember 26. The inner electrode member 24 and the outer electrode member26 are preferably attached to the backing member 14 by a bondingmaterial.

The backing plate 32 and backing ring 34 are preferably made of amaterial that is chemically compatible with process gases used forprocessing semiconductor substrates in the plasma processing chamber,and is electrically and thermally conductive. Exemplary suitablematerials that can be used to make the backing member 14 includealuminum, aluminum alloys, graphite, and SiC.

The upper electrode 12 can be attached to the backing plate 32 and theoptional backing ring 34 with a suitable thermally and electricallyconductive elastomeric bonding material that accommodates thermalstresses, and transfers heat and electrical energy between the upperelectrode 12 and the backing plate 32 and backing ring 34. The use ofelastomers for bonding together surfaces of an electrode assembly isdescribed, for example, in commonly-owned U.S. Pat. No. 6,073,577, whichis incorporated herein by reference in its entirety.

In one embodiment, backing member 14 can be composed of graphite, whichhas a slightly higher coefficient of thermal expansion to silicon, amaterial for the upper electrode 12. The grade of graphite for backingmember 14 has a coefficient of thermal expansion of 4.5×10⁻⁶ (° F.)⁻¹;silicon has a coefficient of thermal expansion of 1.4×10⁻⁶ (° F.)⁻¹. Asa result, the bonding material used to attach the graphite backingmember 14 to the silicon upper electrode 12 is subjected to lowerstresses during thermal cycling of the assembly. However, for certainsituations, a graphite backing member 14 can be less than completelysatisfactory in some embodiments of the showerhead electrode assembly10, because graphite can be an source of particulate contamination,lowering the overall yield of the manufacturing process.

One approach for minimizing the introduction of particulate matter is toreplace graphite with a metallic material (e.g., aluminum, stainlesssteel, copper, molybdenum, or alloys thereof), which provide improvedstability under extreme operating conditions and generates fewerparticles. Metallic components are more cost effective and easier tomachine, in comparison to their non-metallic counterparts. However, inreplacing a graphite backing member 14 with aluminum, for example,additional problems need to be overcome, including: (i) compensating forthe difference in coefficient of thermal expansion in the aluminumbacking member 14 and silicon upper electrode 12; and (ii) interactionsbetween certain process gases and the aluminum.

Fluorine-containing gas (e.g., CF₄, CHF₃) plasmas can be used in plasmaprocess chambers for etching dielectrics or organic materials. Theplasma is composed of partially ionized fluorine gas, including ions,electrons, and other neutral species, such as radicals. However,aluminum chamber hardware, when exposed to low-pressure, high-power,fluorine-containing gas plasma, can produce a significant amount ofaluminum fluoride (i.e., AlF_(x)) byproduct. A process that minimizesaluminum fluoride particles from the chamber hardware would reduce theincidence of defects, chamber processing drift, and/or chamber downtimefor cleaning and maintenance.

Due to the thermal expansion of the backing member 14 and upperelectrode 12, gas passages 28 and 30 move radially relative to eachother and shift positions during heating. For example, the radialmovement of gas passage 28 relative to the center of the circular upperelectrode 12 due to thermal expansion varies depending upon the radialdistance of a particular gas passage 28 from the center of the upperelectrode 12. In other words, upon heating of the upper electrode 12, agas passage near the outer periphery of the upper electrode 12 normallymoves a greater distance relative to the center of the upper electrode12 than a gas passage located near the center. If the backing member 14and upper electrode 12 are constructed of materials with similarcoefficients of thermal expansion (e.g., a graphite backing member 14bonded to a silicon upper electrode 12), gas passages 28 and 30, whichare concentric at room temperature, remain substantially concentric atan elevated process temperature. However, when forming the backingmember 14 and upper electrode 12 of materials with differentcoefficients of thermal expansion, additional complexities occur. Forexample, aluminum has a coefficient of thermal expansion of 14×10⁻⁶ (°F.)⁻¹; silicon has a much smaller coefficient of thermal expansion of1.4×10⁻⁶(° F.)⁻¹. This large difference in coefficient of thermalexpansion may pose additional problems, including misalignment of gaspassages 28 and 30 and accommodating shear stresses that are generatedat the bonded interface when the upper electrode 12 is heated toelevated temperatures.

FIG. 2A illustrates a circular backing member 14, including gas passages30. FIG. 2B is an enlarged view of multiple gas passages 28 and 30 (asindicated in FIG. 2A) which are circular through holes at an ambienttemperature. For this embodiment, the backing member 14 is aluminum andupper electrode 12 is silicon. The dashed arcs 28B, 30B in FIG. 2Brepresent concentric circles passing through the center of gas passages28, 30, respectively, indicating the radial position of each gaspassage. In this particular embodiment, gas passages 28, 30 aremisaligned (i.e., the center of each pair of through hole 28, 30 isnon-concentric or offset) at ambient temperature. For a circular backingmember 14 and a circular upper electrode 12, the degree of misalignmentincreases in the radial direction from the center of the backing member14 and upper electrode 12 to the periphery of these components. However,gas passages 28, 30 are positioned, sized or shaped, such that when thebacking member 14 and upper electrode 12 are heated to a specifiedelevated process temperature (e.g., between about 80° C. and about 160°C.), gas passages 28, 30 are substantially concentric, as illustrated inFIG. 2C. In other words, upon heating, the dashed arcs 28B, 30B in FIG.2B expand radially by different amounts, such that they overlap, as seenin FIG. 2C. In this embodiment, although gas passages 28 and 30 aremisaligned at ambient temperature, the diameter of the through hole inthe aluminum backing member 14 is sufficiently large, such that gaspassages 28 and 30 always overlap between ambient temperature and atelevated temperatures, as seen in FIG. 2.

Upon heating to a maximum process temperature, the gas passages 28, 30become misaligned, as indicated by the radial position of each gaspassage as indicated by the dashed arcs 28D, 30D in FIG. 2D.

In alternate embodiments, the through holes 28, 30 can be non-circularor the like, such as a semi-elliptical or radially elongated, as seen inFIG. 3.

As illustrated in FIGS. 2B and 2C, the gas passage 30 in the aluminumbacking member 14 is larger than the gas passage 28 in the silicon upperelectrode 12. The size of the gas passage 30 is effective to prevent theformation of a plasma within gas passage 30. As described above, theexposure of an aluminum component to fluorine-containing gas plasma cangenerate unwanted aluminum fluoride byproducts. This configuration canadvantageously reduce the exposure of the aluminum backing member 14 toa fluorine ions and/or radicals. During plasma processing, fluorine ionsor radicals may migrate through gas passages 28 and react with aluminum.Thus, a radially larger aluminum through hole configuration increasesthe diffusion length of an ion or radical, reducing the probability ofinteracting with the aluminum backing member 14. In other words, aradially larger aluminum through hole reduces the line of sight fromions or radicals in the plasma to an exposed aluminum surface. Thus, thelarger aluminum through holes can reduce and preferably minimize thegeneration of aluminum fluoride particles in the plasma processingchamber.

In a preferred embodiment of the upper electrode 12 and backing member14, these two components are attached with an elastomeric bondingmaterial 36 as illustrated in FIG. 4. In this embodiment, the backingmember 14 and upper electrode 12 are configured to minimize plasmaattack of the elastomeric bonding material 36. As shown in FIG. 4, anelastomeric bonding material 36 is applied in the interior of annularrecesses 38 that extend into the surface of backing member 14 with thedepth of the recess defined by walls 40. Alternatively, the recesses 38may be located in the upper electrode 12. The outmost walls 40 of therecess 38 can protect the elastomeric bonding material 36 from attack bythe plasma environment in the plasma processing reactor. In theembodiment illustrated in FIG. 4, an electrically conductive member 42is in direct contact with the backing member 14 and upper electrode 12.The conductive member 42 is mounted near the peripheral edge of thebacking member 14 and upper electrode 12 to improve RF conduction.Additionally, the conductive member 42 improves DC conduction betweenthe backing member 14 and upper electrode 12, preventing arcing betweenthese two components. Preferably, the conductive member 42 is flexible,such that the member can accommodate the contraction and expansion dueto thermal cycling of the electrode assembly. For example, the flexibleconductive member 42 can be a spiral metallic gasket (e.g., RF gasket),preferably made of stainless steel or the like.

In another embodiment of the upper electrode 12 and backing member 14,as illustrated in FIG. 5, the backing member 14 comprises a peripheralannular flange 44, and the upper electrode 12 comprises a peripheralannular recess 46 configured to mate with the peripheral annular flange44. This flange 44 reduces exposure of the elastomeric bonding material36 to a plasma environment by shielding the elastomeric bonding material36 from the ions or radicals in the plasma. Additionally, to increasethe amount of contact area between the bonding material and the backingmember 14 and upper electrode 12, bonding surfaces can be roughened ortextured prior to applying the elastomeric bonding material 36.

As described above, when a component, such as the backing member 14 orupper electrode 12, is heated to an elevated processing temperature, theouter portion expands to a greater degree than the central portion. Iftwo components with similar coefficients of thermal expansion are bonded(e.g., a graphite backing member 14 and a silicon upper electrode 12),upon heating, the shear stress applied to the elastomeric bondingmaterial is limited, because both materials undergo a similar amount ofthermal expansion. However, if two components with greater differencesin thermal expansion coefficients are bonded (i.e., aluminum andsilicon), upon heating, a non-uniform shear stress is generated in theelastomeric bonding material 36, due to the different rates of thermalexpansion. For example, if a circular aluminum backing member 14 isconcentrically bonded to a circular silicon upper electrode 12, theshear stress in the elastomeric bonding material 36 near the center ofbacking member 14 and upper electrode 12 is minimal at an elevatedprocessing temperature. However, the outer portion of the aluminumbacking member 14 undergoes a larger amount of thermal expansion thanthe outer portion of the silicon upper electrode 12. As a result, whenthe two materials are bonded, the maximum shear stress occurs in theouter peripheral edge of the backing member 14 or upper electrode 12,where the difference in thermal expansion is greatest.

FIG. 6 illustrates a cross-sectional view of a circular backing member14 bonded to a circular upper electrode 12 with a variable elastomericbonding material 36 thickness (gas passages 28, 30 are not shown). Asshown, the thickness of the elastomeric bonding material 36 is varied,such that the non-uniform thickness is effective to accommodatenon-uniform shear stresses generated by thermal expansion. In theembodiment shown in FIG. 6, the elastomeric bonding material 36 isthinnest near the center of the backing member 14 and upper electrode12, where the shear stress is minimal due to thermal expansion. Incontrast, the elastomeric bonding material 36 is thickest near the outerperipheral edge of backing member 14 and upper electrode 12.

In general, components with smaller dimensions (i.e., less volume)undergo a smaller amount of thermal expansion. For example, a circularaluminum member with a 12 inch diameter expands radially approximately0.027 inches when heated from ambient to 200° C.; a circular aluminummember with a 2 inch diameter expands radially approximately 0.0045inches when heated from ambient to 200° C. Thus, it has been determinedthat by bonding a smaller aluminum member 14 to a silicon upperelectrode 12, the elastomeric bonding material 36 needs to accommodatesignificantly less shear stress. In other words, instead of bonding theupper electrode 12 to a larger, single aluminum backing member 14 havinga continuous surface, the upper electrode 12 can be bonded to multiplesmaller pieces of aluminum (i.e., each having a surface area less thanthe surface area of the electrode it is bonded to), which in which eachindividual piece undergoes a smaller amount of thermal expansion. As aresult, the elastomeric bonding material 36 is subjected to a smallerdegree of shear stress with respect to each individual piece duringthermal expansion.

FIGS. 7A and 7B illustrate two embodiments of the backing member 14 eachof which comprises of multiple pieces (gas passages not shown). Forexample, the backing member 14 is comprised of a circular plate 47 withmultiple concentric annular rings, inner ring 48, middle ring 50, andouter ring 52. as shown in FIG. 7A. Each concentric ring 48, 50, 52 caneither be continuous (not shown) or separate segments arranged in a ringconfiguration. In the embodiment shown in FIG. 7B, the backing member 14is comprised of multiple hexagonal-shaped pieces 54 with outer pieces 54shaped to complete the circular configuration of backing member 14.

In an alternative embodiment, illustrated in FIG. 8, the backing member14 is a single piece with a non-uniform thickness across its width, toimpart flexibility to the backing member 14 during thermal cycling (gaspassages 28, 30 are not shown). Similar to the configuration withmultiple pieces, the thicker segments 56 with the same thickness, ofreduced dimensions are subjected to a smaller degree of thermalexpansion. In this embodiment, the thicker segments 56 such as acircular plate and outer annular sections are connected together bythinner flexure segments 58, such as thin rectilinier or curvedsegments, which are configured to accommodate thermal expansion, thusreducing the shear stress applied to the elastomeric bonding material 36during thermal expansion. In another embodiment, not shown in FIG. 8,concentric or helical grooves can formed in backing member 14 to provideareas to accommodate thermal expansion.

EXAMPLE 1

Tests were performed to determine the effect of the backing member 14material on particle generation during semiconductor wafer processing inan EXELAN® FLEX™ dielectric plasma etch system, manufactured by LamResearch Corporation, located in Fremont, Calif. For these tests, thegeneration of particles over 0.09 μm for an aluminum backing member wascompared with that from a graphite backing member for multiple siliconwafers. The tests were performed by placing a 300 mm silicon wafer in aplasma processing system, similar to the configuration in FIG. 1 andplasma processing the wafer with a process recipe similar to asemiconductor etching process. For multiple tests, the silicon wafersurface was then analyzed with a laser scanning device for the number ofparticles larger than 0.09 μm to obtain the number of particle adders(the difference between the number of particles on the wafer before theplasma process and after the plasma process). As seen in Table 1, thealuminum backing member generated fewer particle adders than thegraphite backing member.

TABLE 1 Backing Member Particle Adders Material (>0.09 μm) (median)Graphite 25 Aluminum 9

While the invention has been described in detail with reference tospecific embodiments thereof, it will be apparent to those skilled inthe art that various changes and modifications can be made, andequivalents employed, without departing from the scope of the appendedclaims.

1. A component for a plasma processing apparatus for processingsemiconductor substrates, the component comprising: a first memberhaving a plurality of first through openings, the first member having aplasma-exposed surface and a first coefficient of thermal expansion, thefirst openings located at different radial positions across the surface;a second member bonded with an elastomeric bonding material to the firstmember and having a plurality of second through openings correspondingto the first openings, the second member having a second coefficient ofthermal expansion greater than the first coefficient of thermalexpansion; wherein the second openings are larger than the firstopenings and centers of the first and second openings are misaligned atambient temperature and the centers of the first and second openingsmove radially and are closer together due to thermal expansion when thefirst and second members are heated to a predetermined elevatedprocessing temperature; wherein: (a) the openings in the first memberand the openings in the second member are substantially concentric whenthe first and second members are heated to the predetermined elevatedprocessing temperature; (b) the second openings reduce the exposure ofthe second member to a plasma environment; (c) the second openings arenon-circular; (d) the second openings are semi-elliptical holes orradially elongated slots; (e) the openings in the first and secondmembers are axially extending gas distribution passages; (f) the secondmember is composed of a metal; (g) the second member is composed ofaluminum, molybdenum, copper, stainless steel, or alloys thereof; or (h)the first member is composed of a non-metallic material.
 2. Thecomponent of claim 1, wherein (a) the first member is silicon and (b)the second member is aluminum.
 3. The component of claim 2, wherein thefirst member is a silicon plate and the second member is an aluminumplate: (a) the elastomeric bonding material is applied in one or morerecesses formed in the first member, each recess having walls adapted toreduce the exposure of the elastomeric bonding material to a plasmaenvironment; (b) the elastomeric bonding material is applied in one ormore recesses formed in the second member, each recess having wallsadapted to reduce the exposure of the elastomeric bonding material to aplasma environment; or (c) the second member comprises an axiallyextending peripheral flange and the first member comprises a peripheralrecess configured to mate with the flange, which is adapted to reduceexposure of the elastomeric bonding material to a plasma environment inthe apparatus.
 4. The component of claim 3, further comprising anelectrically conductive member mounted between and in direct contactwith the first and second members.
 5. The component of claim 4, whereinthe conductive member is composed of an RF gasket material and mountednear a peripheral edge of the first and second members.
 6. The componentof claim 3, wherein: (a) the elastomeric bonding material has a variablethickness effective to compensate for a non-uniform shear stressgenerated in the elastomeric bonding material when heated to thepredetermined elevated processing temperature during processing ofsemiconductor substrates or (b) the first member and second member arecircular plates, concentrically bonded, and the thickness of theelastomeric bonding material is varied in a radial direction of thefirst and second members, the thickness effective to compensate for anon-uniform shear stress generated in the elastomeric bonding materialwhen heated to an elevated processing temperature.
 7. The component ofclaim 1, wherein the second member has a non-uniform thickness acrossits width, adapted to impart flexibility to the second member duringthermal cycling.